Stereological description of the anterior horn cervical cord of the adult rat. A quantitative study using the optical microscope.

Abstract

AbstractThe histometric properties of the most ventral, ventromedial and ventrolateral zones in the anterior horn of adult rat cervical enlargement were studied by quantitative optical microscopy. The spinal cord areas were identified in semi‐thin Araldite sections and unbiased samples of the test tissue were recorded on photomicrographs. By defining the tissue on the basis of a histometric model, it was possible to describe a number of important stereological parameters including compartmental volume proportions, cellular packing densities, perikaryal volumes and surface areas, and blood vessel length per unit volume.It was established that each cubic milimetre of tissue consists of approximately 0.85 mm3 of neuropil, 0.04 mm3 of blood vessels, 0.02 mm3 of neuroglial cells, 0.08 mm3 of motoneuron perikarya and 0.02 mm3 of small neuron perikarya. Roughly 0.11 mm3 of the neuropil compartment can be attributed to myelin. Estimates of cell body packing densities revealed an average of 44,950 neuroglial cells and 11,650 neurons per mm3. Small and motor neurons occur in approximately equal numbers. The average motoneuron has a perikaryal volume of 12,100 μm3 and a perikaryal surface area of 2,500 μm2. Corresponding figures for small neurons are 2,200 μm3 and 650 μm2. The average glial cell soma has a volume of 370 μm3. Differences between the nuclear volume proportions and nuclear size distributions of glial cells, small neurons and motoneurons are also reported. Each mm3 of tissue contains 1.2 metres of blood vessels, of average diameter 6.4 μm and with an outer surface area of 21 mm2.The results are presented and discussed in the context of data published by workers in other laboratories.